Computer systems now commonly include GUI operating systems that employ graphical objects, such as icons, windows, and dialog boxes, to prompt and receive user input. A user typically enters information by positioning a cursor within a designated area of a graphical desktop—e.g., by using a mouse, trackball, finger, stylus, direction keys or the like—to implement a desired function. GUI operating systems, such as MicroSoft® Windows®, have gained widespread acceptance because of their simple, intuitive operation and because they allow easy movement between multiple applications programs.
GUI users have responded to this flexible usability by demanded operating systems with enhanced desktop functionality, i.e., an operating system working area larger than the display area of a single monitor. One way of implementing an enhanced desktop is by utilizing multiple monitors or by employing a virtual desktop area where the display area of a single monitor can be “scrolled” across a larger graphical desktop. Such enhanced desktop systems achieve greater display capability without the expense or inconvenience of a single, larger monitor. Unfortunately, prior GUI operating systems were not specifically adapted for multiple monitor enhanced desktop operation and were often highly hardware dependent.
Solutions to the multiple monitor enhanced desktop problems are described in U.S. Pat. No. 5,835,090 for DESKTOP MANAGER FOR GRAPHICAL USER INTERFACE BASED SYSTEM WITH ENHANCED DESKTOP, which is assigned to the assignee of this application and is incorporated herein by reference. However, GUI operating systems and graphics-intensive applications running on them require considerable computer processing power. Indeed, the performance demands of users and graphic application developers have outstripped the performance capabilities of most processors, especially when operating a multiple monitor GUI operating system.
MicroSoft® has addressed many of the performance aspects of application programs by developing the DirectX® family of application program interfaces (“APIs”), which provide Windows-based software applications with direct access to display hardware resources. DirectX provides developers with a common set of instructions and software “components” that allow applications, such as multimedia applications, to run on any Windows-based personal computer (“PC”) while ensuring that the applications take full advantage of any high-performance hardware capabilities to achieve the best possible performance.
DirectX® includes a wide variety of multimedia enabling technologies including DirectDraw®, Direct3D®, DirectInput®, DirectSound®, DirectPlay®, DirectMusic™, DirectShow™, and DirectAnimation™ to optimize the displaying graphics and video information. The DirectX Foundation layer components, DirectDraw and Direct3D, are of general importance, and the Media layer component, DirectShow, is importance for displaying graphics and video, particularly streaming video applications. In general, DirectX components have enabled the development of a new generation of high-performance gaming and video applications through the use of DirectDraw, Direct3D, and DirectShow calls.
Unfortunately, DirectX APIs running under Windows 95 and Windows NT 4.0 assume a single display monitor and are, therefore, incompatible with systems driving multiple monitors. More specifically, DirectX and applications written to DirectX, assume that only one graphics frame buffer is available for driving the single monitor. In DirectX, a complex sequence of calls (simply referred to hereafter as “GetFrameBufferAddress”) allow DirectX applications to locate and access the single frame buffer. Graphic device drivers must support the GetFrameBufferAddress calls because they are used to write data directly into frame buffer memory, bypassing the typical Graphic Device Interface (“GDI”) and, thereby, providing accelerated performance.
However, the graphics device driver can return only a single frame buffer address in response to the GetFrameBufferAddress calls, and most multiple monitor driver cards employ two or more frame buffers to implement multiple monitor displays. This begs the question, which of the two addresses does the multiple monitor device driver return? If the driver returns the address of the first frame buffer and the DirectX application is displaying through another frame buffer, or vice versa, display errors will occur. The alternative is to sacrifice hardware acceleration and employ the GDI to perform DirectX operations with processor resources, which dramatically increases processor utilization and decreases performance.